Electric furnace and method of operation



L. c. H. GROEGER. ELECTRIC FURNACE AND M THOD OF OPERATION.

APPLICATION FILED APR. 5, 1919.

- Patented Mar. 16, 1920.

2 SHEETS-SHEET I.

L. C. H. GROEGER.

ELECTRIC FURNACE AND METHOD'OF OPERATION.

APPLICATION FILED APR.-5, I919.

Patented Mar. 16, 1920.

2 SHEETS-SHEET 2.

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LOUIS C. H. GROEGER, OF CHICAGO, ILLINOIS.

ELECTRIC FURNACE AND METHOD OF OPERATION.

Specification of Letters Patent. Patented Mar. 16, 1920.

Application flled.April 5, 1919. Serial No. 287,695.

To all 'ugfiom it may concern.-

Be it known that I, LOUIS C. H. Gmonena,

ing is a specification.

This invention relates particularly to electric furriacesadapted to operate normally with electric current passing between upper electrodes and a wall or hearth contact and through the interposed charge, which preferably is fused by the arcing of the electric current.

The primary object is to provide an electric furnace capable of being operated by several different methods, whereby improved results can be obtained. A further object is to provide an improved general method of operation which possesses distinctive advantages.

The invention is illustrated in its preferred embodiment in the accompanying drawings, in which Figure 1 represents .a sectional view of an electric furnace in the preferred form.

embodying the invention, the view being more or less diagrammatic, the furnace having the electrodes adjusted to operate as a two-phase furnace; Fig. 2, a similar section, showing the furnace operating as a three-phase furnace, as, for example, in preliminarily heating the furnace; Fig. 3, a similar view showing the furnace operating as a single-phase furnace, as where it is desired to hold the heat, for example, while a chemical analysis of the metal is being made; Fig. 4:, a similar view showing a modification of the furnace operating as a two-phase furnace; and Fig. 5, a broken sectional view showing a modification of the hearth contact.

In the construction illustrated in Figs. 1 to 3. inclusive, A represents the body of the furnace provided with a heating, or melting chamber, A, and a hearth A B, B, a pair of side electrodes which are disposed opposite each other and extend through the side walls of the furnace; B an upper electrode which extends through the top wall of the furnace; C, C, the secondary coils of a transformer device, or pair of transformers, said coils having the terminals at one end connected with a common, or neutral, conductor D, and having the other terminal contablishing the arc.

nected with conductors D, D E, E, the primary coils of the transformer device, or pair of transformers; F, a conductor, equipped with a switch F, adapted to connect adjacent terminals of the coils E and E; G, a conductor, equipped with a switch G, said conductor G serving as a 50% tap for the coil E and an 86.6% tap for the coil E; H, and H, conductors connected with the outside terminals of the coils E and E; and H a common, central, or return conductor connected with the conductor F; and I, J, and K, electric power supply lines adapted to be connected, by switches L, with the conductors H, H and H, respectively. The conductors D, D and D are equipped with reactance coils M which may be used in starting operations, and may be cut out of the circuits by switchesM after stabilized operation has been established.

The conductor D connects with the upper electrode B the conductor D connects with the side electrode B; and the conductor D connects with the side electrode B.

The conductor D has a branch conductor 1 which leads to a terminal 1 the conductor 7 1 being for use in two-phase operation of the furnace (as in Figs. 1 and 4).

The conductor D has a branch conductor 2 which leads to a terminal 2*, the conductor 2 being in use in single-phase operation of the furnace (in accordance with Fig. 3).

The hearth A of the furnace is lined with suitable refractory material, which may be relatively nonconductive when cold and conductive when hot, or which may be conductive when cold and hot.

The hearth is provided with a contact, or terminal N. with which is connected a conductor 3 which is equipped with a switch '3. which may serve to connect the conductor 3 with the branch conductor 1, or the branch conductor 2, as desired.

Any suitable construction may be em.- ployed, provision being made for keeping the electrodes insulated with respect to each other.

The side electrodes B and B are tiltably mounted to enable them to be swung toward and away from the charge, or bathfP; and the side electrodes are also longitudinallv adjustable to enable their inner ends to be brought together and then separated in es- Each of the side electrodes is preferably carried by an electrode clamp 4 mounted on a tiltable arm, or memher, 5, and adjustable toward and away from the furnace by mechanism 6, the details of I, which are unimportant and not. shown.

The electrodes B and B project freely through slots 7 in the side walls of the furnace, and said electrodes are equipped with suitable cooling devices 8 which practicall close the openin vertically somew at, if necessary.

In the illustration given, the electrodesupports 5 are connected by pivots 9 to brackets carried by the side walls of the furnace; and the outer ends of the members 5 are equipped with racks 10 operated by gear-trains l1 and electric motors 12.

The upper electrode 13 is preferably disposed centrally and isadjustable vertically, so that it may be lowered into contact with the inner ends of the side electrodes when the latter are brought together, this arrangethat it can be swung slightly in any direction, in adjusting the electrodes, so that they will meet properly at their inner ends.

The electrode B is shown provided with a cooling device 13 and clamping and adjusting means 1-} supported by brackets 15 mounted on the top of the furnace. No detail is shown, as any suitable means may be employed.

Assuming the switehesL to be closed, and

assuming the switches M to be open until the operation is established, and then closed, the preliminary heating of the furnace may be effected, for instance, with the electrodes adjusted in the manner shown in Fig. 2.

To secure a three-phase operation with the electrodes so adjusted, the switches 3 and G are left open and the switch F is closed.

The current from the secondary coils thus passes through the neutral wire D and the wires 1) and wires D the three electrodes taking part in the operation, the furnace operating on the three-phase open delta system. This same arrangement may be employed in burning in the hearth of the furnace, except that the side electrodes will be tilted downwardly so as to be as close as possible to the hearth, and the-upper electrode being correspondingly lowered, whereby a three-phase free-burning arc is maintained close to the hearth.

Assuming the furnace to have been properly preheated (by a previous operation, or operating in the manner described s 7, and which may shi t above), the hearth will be conductive, even if composed of refractory material which is relatively non-conductive when cold.

The furnace may then be operated as a twophase furnace, with the electrodes ad usted 1n the manner shown in Fig. 1. In this operation, the switch F is left open, the switch G is closed and the switch 3 is on the contact 1, that is, connected with the branchconductor 1. Thus, the conductive hearth is in circuit with the conductor D leading to the neutral point of the secondary windings of the transformer device; and the current circulates through the side electrodes, the bath, the conductor 3, and branch conductor 1 of the central conductor D.

This last described mode of operation is also employed in connection with furnace arranged as shown in Fig. 4.

From the description thus far given, it will be understood that the first melting of the charge may be effected by means of a free-burning are between the electrodes above the charge, and that the arc may then be established between the'electrodes and the bath, the current passing through the bath and through the hearth of the furnace. This overcomes the objections incident to establishing an arc between the electrodes and the charge at the outset, it being understood that the charge does not provide a sufliciently good conductive medium at the outset to enable the operation of the furnace to be readily stabilized. In passing current through the charge, or through the upper portion of the charge, as a path between the electrodes, more or less arcing will occur between the pieces which constitute the charge,

causing fluctuations in the load and generally unsatisfactory operation.

The present invention enables these difiiculties to be obviated, and enables a freeburning arc to be employed in the first or preliminary reduction of the charge, and then enables the are to be transferred so as to pass between the electrodes and the bath when the bath is in such condition as to properly conduct the current. Thus, the normal operation of the furnace can be carried on through the hearth with consequent .economy in the use of power, and with the resultant circulation of the molten metal, which tends to the production of uniform guality throughout the body of the metal. 11 case the furnace tends to become too hot, or in the event that it is desired to hold the heat, as,-f 'or instance, during the time required to make a chemical analysis, the side electrodes may be withdrawn, the upper electrode lowered, and an arc established between the upper electrode and the bath in the manner illustrated in Fig. 3, the furnace now operating as a single-phase furnace and employing only the transformers E, C. In this operation, the switches F- and G are tends to economy of operation, as wellas to a the' avoldance of overheating. Also, this be employed; and any suitable trans ormer spirit of my invention.

The foregoing detailed description has left open, and the switch 3 connected with the branch conductor 2. Thus, a circuitis established from thecoils C throu h the branch conductor 2, the conductor 3, t e hearth, the bath, the electrodeB and the conductor D. It will be understood that this provision enables the heat to be flield while chemical analyses are being the exact condition of the metal in the bath may be known.

In the modification shown in. Fig. 4, the construction is similar to the construction shown in Fig. 1, except that the bodyA of the furnace is for med without an open-. ting-in the top, and the upper-electrode B i is omitted. Corresponding parts in Fig; 1 are indicated by a reference character shown in Fig. 1.

Inthe modification shown'in Fig. 5, the hearth A is shown provided with a contact, or electrode, A, of carbon or metal. This form of electrode may be employed either,

in the construction shown in Fig. 1 or in the construction shown in Fig. 4.

From the description given, the advantages of the improved furnace will be readily understood by those skilled in the art.-

Any suitable source of power'suppl may means may be employed, where transformer devices are desired.

With the transformer device, the electric circuits and the switches arranged as-illus-- trated, the furnace may be operated as a single-phase furnace, a two-phase furnace,

or a three-phase furnace; and the capability of the furnace for ready conversion to these different methods of operation possesses distinct advantages, many of which have been pointed out. ever, that a great variety of modifications of the transformer devices and connectionsmay be made, without departing from the been given for clearness of understanding only, and no unnecessary limitation should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view'of the prior art.

What I claim as new, and desire to secure by Letters Patent, is:

1. In an electric furnace, the combination of a heating chamber having a hearth terminal, a plurality of co-acting side electrodes extending towardeach other from the sides of the furnace. and so disposed above the bath as to enable an arc to be established directly betweentheir inner ends, said electrodes being tiltable, adjusting means adapted to vary the tilt of said electrodes, and means whereby circuits may be established with an are directly between the elecmade, so that It will be understood, how

trodes or with an are between: the electrodes and the bath with the circuit completed throu h the hearth terminal;

'2. of a heating chamber having a hearth terminal, a. pair of tiltably mounted "side electrodes disposed opposite each other and an electric furnace, the combination adapted to have their inner ends brought together and then'separated to establish a dlrect are between the electrodes, a source ofelectric current, and means vwhereby the furnace may be'caused to operate with an are directly between said electrodes, or. with be established directlybetween their inner ends, an upper electrode extending through the top wall of the furnace and so disposed and mounted that its inner end can be brought into contact with the inner ends of the side electrodes, a source of electric 1 energy, and means ..Whereby' a free-burning arc maybe established between the side electrodes andupper electrode and whereby an arc may be afterward established between the side-electrodes and "the bath with the cir-- cuit completed through the hearth terminal,

4. In anelectric furnace, the combination of a heating chamber having a hearth termina1, -a plurality of side electrodes so disposed above the bath as toenable an arc to be established directly between their inner ends,- an upper electrode extending through the top of the heating chamber and adapted to have its inner end brought into contact with the inner ends of said side electrodes, a source of electric energy, and connections and switches, whereby the furnace may be operated with an arc between-all three electrodes,'or with an' are between the side electrodes and the bath, or with an are between the upper electrode and the bath.

5. In an electric furnace, the combination of a heating chamber having a hearth terminal, a plurality of side electrodes extending through the side walls of said heatits-inner end brought substantially into contact with the inner ends of said side elec-' trodes, and transformer means, circuits and switches, whereby said three electrodes may operate with a free-burning are between them in a three-phase'system, or whereby said side electrodes may operate with an are between them and the 'bath with the circuit completed through the hearth terminal per electrode may operate with an are between it and the bath with the circuit completed through a hearth terminal in a singlephase system.

6. In an electric furnace, the combination of a heating chamber having a hearth terminal, three electrodes disposed above the bath and adapted to have their inner ends brought substantially into contact to enable an arc to be established, two of said electrodes projecting toward each other from the sides of the furnace and the third electrode depending through the top of the furnace, and transformer means, connections and switches, whereby the furnace may be operated with a free burning arc directly between the electrodes, or may be operated with an are between the side electrodes and the bath, with the circuit completed through the hearth terminal.

7. In an electric furnace, the combination of a heating chamber having a hearth ter-- minal, three electrodes-disposed above the bath and adapted to have their inner ends brought substantially into contact to enable an arc to be established, and transformer means, connections, and switches, wherebythe furnace may be operated as a threephase furnace, a two-phase furnace, or a single-phase furnace.

8. In an electric furnace, the combination.

of a heating chamber having a hearth terminal, a pair of tiltable electrodes disposed opposite to each other and projecting through the side walls of the furnace, an ad ustable upper electrode depending through the top wall of the furnace, transformer means having a pairof secondary coils, a conductor connecting one terminal of each of said coils with said upper electrode, conductors connecting the other terminals of said coils with the side electrodes, said first-named conductor having a. branch conductor connected therewith, a conductor connected with the hearth terminal, and means for connecting said last-named conductor with said branch conductor.

9. In an electric furnace, the combination of a heating chamber having a hearth terminal, 'a pair of tiltable electrodes disposed opposite to each other and projecting through the side walls of the furnace,

an adjustable upper electrode depending through the top wall of the furnace, transformer means having a pair of secondary coils, a conductor connecting one terminal of each of said coils with said upper electrode, conductors connecting the other terminals of said coils with the side electrodes, said first-named conductor having a branch conductor connected therewith, a conductor connected with the hearth terminal, a

branch conductor leading from one of the conductors connected. with a side electrode, and a switch adapted to connect the conducsides of said chamber, adjustable side elec-- trodes mounted on said arms and extending through. the side walls of the furnace, mechanism for turning said arms about their pivots to vary the inclination of said side electrodes, and a source of electric en ergy connected with said electrodes.

11. In an electric furnace, the combination of a heating chamber, a pair of pivotally-mounted arms disposed at opposite sides of said chamber, adjustable side electrodes mounted on said arms and extending through the side walls of the furnace, racks depending from said arms, motor devices geared to said racks, anda source of electric energy connected with "said electrodes.

i 12. In an electric furnace, the combination of a heating chamber provided with a hearth contact, a pair of swinging adjustable side electrodes located directly opposite each other, an adjustable upper electrode depending through the top wall of the" heating chamber, a source of electric energy, and means whereby either said side electrodes or said upper electrode may be caused to operate with an are through the tion of a heating chambenprovided with a hearth contact, a pair of swinging adjustable side electrodes located directly opposite each other, an adjustable upper electrode depending through the top wall of the heating chamber, a source of electric energy, and means whereby said three electrodes may be caused tooperate with an are directly between them as a three-phase system, or whereby saidside'electrodes may be caused to operate with :an are between them and the bath, with the circuit completed through the hearth terminal, or whereby said upper electrode may be caused to operate with an arc to the bath and with the circuit completed throughsaid hearth terminal. I

, 14. The method of heating an electric furnace which comprises: causing an arc directly between the inner ends of three electrodes then establishing a circuit be-' tween the inner ends of two of said elec trodes and the bath to the hearth and operating with arcs between said two electrodes .and bath.

trodes and the bath to the hearth, operating with arcs between said two electrodes and bath and then withdrawing said two electrodes and operating with an are between the third e ectrode and the bath'with the circuit completed through the hearth.

16. The method of heating and regulating the heat of a furnace which comprises:

operating with an are between the inner ends of two.oppositel disposed electrodes 10' and the bath with t e circuit completed through the hearth; and then withdrawing said electrodes and operating with an are between a thirdel'ectrode and the bath with I the circuit completed through the hearth. 15

LOUISC. H. GROEGER. 

